Consider this code:
<UserControl x:Class="MyApp.MyControl"
...
xmlns:local="clr-namespace:MyApp"
DataContext="{Binding RelativeSource={RelativeSource Mode=Self}}">
<UserControl.Template>
<ControlTemplate>
<ControlTemplate.Resources>
<Storyboard x:Key="MyStory">
<ColorAnimationUsingKeyFrames Storyboard.TargetProperty="(Border.BorderBrush).(SolidColorBrush.Color)" Storyboard.TargetName="brdBase">
<SplineColorKeyFrame KeyTime="0:0:1" Value="Red"/>
</ColorAnimationUsingKeyFrames>
</Storyboard>
</ControlTemplate.Resources>
<Border x:Name="brdBase" BorderThickness="1" BorderBrush="Cyan" Background="Black">
...
</Border>
<ControlTemplate.Triggers>
<Trigger SourceName="brdBase" Property="IsMouseOver" Value="True">
<Trigger.EnterActions>
<BeginStoryboard Storyboard="{StaticResource MyStory}"/>
</Trigger.EnterActions>
</Trigger>
</ControlTemplate.Triggers>
</ControlTemplate>
</UserControl.Template>
</UserControl>
The above code works with no problem. Now, I wanna bind key-frame value of MyStory to a DP (named SpecialColor) of this user-control like so:
<Storyboard x:Key="MyStory">
<ColorAnimationUsingKeyFrames Storyboard.TargetProperty="(Border.BorderBrush).(SolidColorBrush.Color)" Storyboard.TargetName="brdBase">
<SplineColorKeyFrame KeyTime="0:0:1" Value="{Binding RelativeSource={RelativeSource Mode=FindAncestor, AncestorType={x:Type local:MyControl}}, Path=SpecialColor}"/>
</ColorAnimationUsingKeyFrames>
</Storyboard>
which makes an error:
Cannot freeze this Storyboard timeline tree for use across threads.
It's possible to do this using code behind. But how can I do it in XAML only?
Code-Behind Aided Solution:
►Step 1: Putting the MyStory storyboard into the brdBase resources.
<UserControl.Template>
<ControlTemplate>
<Border x:Name="brdBase" BorderThickness="1" BorderBrush="Cyan" Background="Black">
<Border.Resources>
<Storyboard x:Key="MyStory">
<ColorAnimationUsingKeyFrames Storyboard.TargetProperty="(Border.BorderBrush).(SolidColorBrush.Color)" Storyboard.TargetName="brdBase">
<SplineColorKeyFrame KeyTime="0:0:1" Value="{Binding RelativeSource={RelativeSource Mode=FindAncestor, AncestorType={x:Type local:MyControl}}, Path=SpecialColor}"/>
</ColorAnimationUsingKeyFrames>
</Storyboard>
</Border.Resources>
...
</Border>
<ControlTemplate.Triggers>
<Trigger SourceName="brdBase" Property="IsMouseOver" Value="True">
<Trigger.EnterActions>
<BeginStoryboard Storyboard="{StaticResource MyStory}"/>
</Trigger.EnterActions>
</Trigger>
</ControlTemplate.Triggers>
</ControlTemplate>
</UserControl.Template>
Error: Cannot find resource named 'MyStory'. Resource names are case sensitive.
►Step 2: Eliminating Trigger on IsMouseOver property and begin the MyStory from code behind.
<UserControl.Template>
<ControlTemplate>
<Border x:Name="brdBase" BorderThickness="1" BorderBrush="Cyan" Background="Black" MouseEnter="brdBase_MouseEnter">
<Border.Resources>
<Storyboard x:Key="MyStory">
<ColorAnimationUsingKeyFrames Storyboard.TargetProperty="(Border.BorderBrush).(SolidColorBrush.Color)" Storyboard.TargetName="brdBase">
<SplineColorKeyFrame KeyTime="0:0:1" Value="{Binding RelativeSource={RelativeSource Mode=FindAncestor, AncestorType={x:Type local:MyControl}}, Path=SpecialColor}"/>
</ColorAnimationUsingKeyFrames>
</Storyboard>
</Border.Resources>
</Border>
</ControlTemplate>
</UserControl.Template>
C# Code-Behind:
private void brdBase_MouseEnter(object sender, MouseEventArgs e)
{
Border grdRoot = (Border)this.Template.FindName("brdBase", this);
Storyboard story = grdRoot.Resources["MyStory"] as Storyboard;
story.Begin(this, this.Template);
}
►Step 3: The solution is already done, but it doesn't work at the first time. Fortunately, there is a workaround for this issue. It's enough to put the ControlTemplate in a Style.
(I need other Trigger types than EventTrigger and must wrap the UserControl elements with the ControlTemplate.)
Update:
The idea about using ObjectDataProvider failed.
- An ObjectDataProvider resource cannot be used to provide a storyboard!!! The error report is:
- XamlParseException: Set property 'System.Windows.Media.Animation.BeginStoryboard.Storyboard' threw an exception.
- InnerException: 'System.Windows.Data.ObjectDataProvider' is not a valid value for property 'Storyboard'.
- The AssociatedControl DP is always null.
Here is the code:
<UserControl.Template>
<ControlTemplate>
<ControlTemplate.Resources>
<local:StoryboardFinder x:Key="StoryboardFinder1" AssociatedControl="{Binding ElementName=brdBase}"/>
<ObjectDataProvider x:Key="dataProvider" ObjectInstance="{StaticResource StoryboardFinder1}" MethodName="Finder">
<ObjectDataProvider.MethodParameters>
<sys:String>MyStory</sys:String>
</ObjectDataProvider.MethodParameters>
</ObjectDataProvider>
</ControlTemplate.Resources>
<Border x:Name="brdBase" BorderThickness="1" BorderBrush="Cyan" Background="Black">
<Border.Resources>
<Storyboard x:Key="MyStory">
<ColorAnimationUsingKeyFrames Storyboard.TargetProperty="(Border.BorderBrush).(SolidColorBrush.Color)" Storyboard.TargetName="brdBase">
<SplineColorKeyFrame KeyTime="0:0:1" Value="{Binding RelativeSource={RelativeSource Mode=FindAncestor, AncestorType={x:Type local:MyControl}}, Path=SpecialColor}"/>
</ColorAnimationUsingKeyFrames>
</Storyboard>
</Border.Resources>
...
</Border>
<ControlTemplate.Triggers>
<Trigger SourceName="brdBase" Property="IsMouseOver" Value="True">
<Trigger.EnterActions>
<BeginStoryboard Storyboard="{StaticResource dataProvider}"/>
</Trigger.EnterActions>
</Trigger>
</ControlTemplate.Triggers>
</ControlTemplate>
</UserControl.Template>
The StoryboardFinder class:
public class StoryboardFinder : DependencyObject
{
#region ________________________________________ AssociatedControl
public Control AssociatedControl
{
get { return (Control)GetValue(AssociatedControlProperty); }
set { SetValue(AssociatedControlProperty, value); }
}
public static readonly DependencyProperty AssociatedControlProperty =
DependencyProperty.Register("AssociatedControl",
typeof(Control),
typeof(StoryboardFinder),
new FrameworkPropertyMetadata(null, FrameworkPropertyMetadataOptions.None));
#endregion
public Storyboard Finder(string resourceName)
{
//
// Associated control is always null :(
//
return new Storyboard();
}
}
Best Answer
Well, you can't really bind to "To" nor From, because the storyboard has to be frozen, in order to work efficiently with cross-threading.
Solution1) Simplest solution without hacks(involves code-behind): Add MouseOver event handler & in the event handler, locate necessary animation, set the "To" property directly, so you won't use binding and the "freezing" can be done. This way you won't hardcode anything :).
Solution2) There is a cool hack that supports XAML only( a little bit of converter magic ofcourse ), but I do not suggest it. It's cool nonetheless :) WPF animation: binding to the "To" attribute of storyboard animation See answer by Jason.
There are few things more that you can try:
Solution3) Don't use Dependency properties, but rather implement INotifyProperthChanged. This way you still can BIND "To". Note that I think this should theoretically work, but I have not tried.
Solution4) Apply Mode=OneTime to your binding. Maybe it works?
Solution5) Write your own attached behavior that will evaluate dependency property on correct thread and set "To" property. I think that will be nice solution.
Here is good duplicate too: WPF Animation "Cannot freeze this Storyboard timeline tree for use across threads"